The currently used amorphous silicon thin film transistors, IGZO (indium gallium zinc oxide) thin film transistors and the like are sensitive to light, due to the electrical properties of light drift and change occurs, so need to cover the active layer with opaque metal layer in the preparation process to reduce the impact of light, making the display device aperture ratio greatly reduced.
In view of carbon nanotubes and graphene and other carbon materials in the structure of carbon atoms were presented as carbon atoms to sp2 hybrid hexagonal ring structure of lamellar structure, has excellent electrical properties, mechanical properties and chemical stability, can be applied to high-frequency devices to improve the frequency response of the device range, can also replace the traditional silicon-based semiconductor devices, prepared into high mobility, transparent, flexible curly thin film transistor. Compared with traditional silicon-based semiconductors and other III-V series semiconductors, carbon materials such as carbon nanotubes and graphene have obvious advantages in the application of flexible transparent thin film transistors because of their advantages of high mobility, high optical transparency, long-term electrical stability and good mechanical bending properties.
However, in the production of thin film transistors, carbon materials such as carbon nanotubes and graphene are affected by factors such as preparation method, dispersion solvent, semiconductor purity, and film formation method, so that the work function of the active layer formed of carbon materials such as carbon nanotubes and graphene fluctuate between 4.2 eV and 5.2 eV. As we all know, the active layer is matched with the work function of the conductive metal. Reducing the contact resistance to form the ohmic contact is a guarantee for the excellent performance of the transistor device. However, the contact between the active layer formed by the carbon materials such as carbon nanotubes and graphene and the metal electrode is not perfect ohmic contact. For example, conductive metal such as metal titanium Ti, metal palladium Pd, metal gold Au and metal platinum Pt are brought into contact with the carbon nanotubes. Their work functions are close to those of the carbon nanotubes. Even though the contact resistance between the metal platinum Pt and the carbon nanotubes is the smallest, the potential barrier still exists. Therefore, using the same adjustable work function conductive metal oxide (work function between 4.0 eV˜6.1 eV) for the work function matching is of great significance.